The front end of a firearm (or the muzzle end of the barrel) tends to rise after firing. This occurs primarily because, for most firearms, the center line of the barrel is positioned above a center of contact established between the shooter and the firearm's grips or stock. The reactive force, or the recoil force, created when a bullet is fired and propellant gases, or propulsion gases, exit the muzzle, acts directly along the center line of the barrel and toward the rear of the firearm, where the shooter is generally positioned. When this line of force is above the center of contact between the shooter and the firearm, the force creates a “moment,” or a rotational force, about the center of contact between the shooter and the firearm, which causes the firearm to rotate about the center of contact such that the muzzle end of the firearm rises upward. Such muzzle rise, or muzzle climb, is particularly evident for firearms having gripping features (e.g., a stock or grip) arranged such that a vertical distance (i.e., the moment arm) between the center line of the barrel and a center of contact with the shooter is particularly large.
A muzzle brake is a device connected to or on the muzzle of the barrel that redirects propellant gases to counter recoil forces. This may be accomplished in two general ways. First, a muzzle brake may present a surface against which the propellant gases impact, causing that transferred force to pull the barrel forward, counteracting part of the recoil forces. Second, redirection of propellant gases laterally, or even somewhat rearwardly, reduce or neutralize the effect of the muzzle blast.
In other cases, a muzzle attachment or porting that is provided along the top of the barrel or that is otherwise upwardly directed, used in combination with minimal or absent redirection or porting that is downwardly directed, exerts a downward force on the muzzle end of the barrel that at least partially counteracts the muzzle rise or muzzle climb described above. Such muzzle devices, whether a muzzle brake, flash suppressor, or compensator, include outlet ports that are asymmetric from top to bottom, about an imaginary horizontal plane. That is, porting is minimized or absent along the bottom of the device and is maximized toward the top and/or sides of the device. The porting in such devices, however, is symmetrical left to right, about an imaginary vertical plane.
Although not previously recognized, and generally not perceived by shooters, the muzzle rise or muzzle climb is not solely in an upward direction. For a right handed shooter, the muzzle rise or muzzle climb includes a vector somewhat to the right (from the shooter's perspective) of directly “up.” Accordingly, after firing a shot, the shooter must move the muzzle downwardly and slightly to the left to realign with the target. Even with very effective compensators having left-to-right symmetrical porting that nearly eliminates muzzle rise or muzzle climb, some movement toward the left (again, for right handed shooters) is required to realign the barrel and sites on the target. Causes may include the ergonomics of how a firearm is typically held by a shooter, the effect of rifling (which usually spins the projectile in a right handed direction), and the cycling of an auto-loading action (including rotation and reciprocation of the bolt and ejection of a spent ammunition casing).